The present invention generally relates to control valves and, more particularly, relates to a dual mode control valve wherein one mode is capable of reducing the energy consumption thereof by regulating a pressure at an output port.
As is well known in the art, control valves have frequently been used to control and supply a working fluid, such as air, to a working device. Typically, these control valves employ a moveable valve spool disposed in a valve housing. The valve housing includes a plurality of fluid passages that are selectively interconnected in response to movement of the valve spool so as to control the flow of the fluid and, thus, the output of the control valve.
Conventional control valves often employ a solenoid valve mounted thereto for actuating the valve spool. The solenoid valve is controlled via an electrical input signal between a first position, where the solenoid valve is de-energized so as to close a fluid passage between an input pilot pressure and an output controlling pressure and to open the outlet to atmosphere, and a second position, where the solenoid is energized via the electrical input so as to open a passageway between the input pilot pressure and the output controlling pressure and block the fluid passage from outlet to exhaust.
It should be readily appreciated to one skilled in the art that in order to apply a constant controlling pressure, the electrical control signal must continue to energize the solenoid valve. That is, in order for a conventional control valve to maintain the spool in a predetermined position, it is necessary to maintain a constant control pressure upon one side of the spool. Therefore, in order to maintain this constant control pressure on the spool, it is necessary to maintain the solenoid valve in an opened and, thus, energized state. Moreover, it is necessary to employ full line fluid pressure to displace and maintain the working device in a predetermined position. Therefore, it will be understood that operating a device at full line pressure requires more energy to drive compressors than operating the device at a reduced line pressure.
Accordingly, there exists a need in the relevant art to provide a control valve capable of producing an output of working fluid to be used with a conventional working device that is capable of minimizing the energy consumed during actuation. Furthermore, there exists a need in the relevant art to provide a control valve that maintains the position of a control element at a pressure less than full line pressure. In certain valve applications, however, it may still be desirable to operate a valve in the standard mode wherein full line pressure is consumed at all times. Thus, there exists a need in the relevant art to provide valves capable of either an energy saver mode or a standard mode while minimizing manufacturing and inventory stocking costs associated with multiple valve types.
A control valve system having an advantageous construction is provided. The control valve system includes a housing having an inlet port, a first output port, a second output port, and a valve chamber. A primary spool has first and second longitudinal ends with respective working surface areas being substantially equal, wherein the primary spool is slidable in the valve chamber to a first position where fluid communication is established between the inlet port and the first output port, a second position where fluid communication is established between the inlet port and the second output port, and an intermediate third position where fluid communication is generally prevented between the inlet port and both of the first and second output ports. A secondary spool is independently slidable in the valve chamber and has a first end for abutting against the second end of the primary spool and has a second end with a working surface area greater than the other working surface areas. A solenoid valve assembly is positionable in a first position for providing fluid communication from the inlet port to the second end of the secondary spool to move the primary spool from the first position to the second position, and in a second position to isolate the inlet port from the second end of the secondary spool. A biaser provides a biasing force to the primary spool in a direction toward the first position which has a predetermined magnitude when the primary spool is in the third position. A first fluid passage through the primary spool provides fluid communication between the first output port and the second end of the primary spool for displacing the primary spool relative to the secondary spool in an energy saving mode when the solenoid valve is in the second position, thereby regulating a pressure at the first output relative to the predetermined magnitude of the biasing force.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.